Module: StoryTeller::Snapshots

Defined in:
lib/story_teller/snapshots.rb

Overview

The Snapshots module

Constant Summary collapse

GzipMagicBytes = 
[0x1F, 0x8B].freeze
TableExclusions =

Adjust exclusions as needed

%i[
  schema_migrations
  ar_internal_metadata
  sequel_migrations
].freeze
SelectSerialSequence =

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'SELECT pg_get_serial_sequence(?, ?) AS seq'.freeze
SelectSetvalTemplate = 
'SELECT setval(%<sequence>s, %<max_id>s, true)'.freeze

Class Method Summary collapse

Class Method Details

.denormalize_row(db, table, row) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 220

def denormalize_row(db, table, row)
  schema = db.schema(table)
  types = schema.to_h.transform_values { |info| info[:type] }

  out = {}
  row.each do |k, v|
    type = types[k.to_sym]
    out[k.to_sym] = parse_value(v, type)
  end
  out
end

.export_to_file(filename) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 284

def export_to_file(filename)
  db = Sequel::Model.db
  tables = ordered_world_tables(db)

  tables_payload = tables.map do |table|
    pk = primary_key_for_table(db, table)
    s_fk = self_fk_column(db, table)

    rows = db[table].all
    # Stable base order, then parent-first for self-FK if applicable.
    rows = rows.sort_by { |r| r[pk] || 0 } if pk
    rows = order_rows_by_self_fk(rows, pk, s_fk)
    rows = rows.map { |r| normalize_row(r) }

    {
      name: table.to_s,
      primary_key: pk&.to_s,
      self_foreign_key: s_fk&.to_s,
      rows: rows
    }
  end

  data = {
    version: 1,
    created_at: Time.now.utc.iso8601,
    tables: tables_payload
  }

  File.open(filename, 'wb') do |file|
    Zlib::GzipWriter.wrap(file) { |gz| gz.write(JSON.generate(data)) }
  end

  filename
end

.gzipped?(filename) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/story_teller/snapshots.rb', line 65

def gzipped?(filename)
  File.binread(filename, 2).bytes == GzipMagicBytes
end

.import_from_file(filename) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 345

def import_from_file(filename)
  db = Sequel::Model.db
  data = read_snapshot_file(filename)

  unless data[:version] == 1
    raise "Unsupported snapshot version: #{data[:version].inspect}"
  end

  snapshot_tables = Array(data[:tables])
  table_rows_by_name = snapshot_tables.to_h do |t|
    [t[:name].to_s, Array(t[:rows])]
  end

  table_syms = snapshot_tables.map { |t| t[:name].to_sym }
  ordered = ordered_world_tables(db, only_tables: table_syms)

  db.transaction do
    truncate_tables(db, ordered)

    ordered.each do |table|
      rows = table_rows_by_name[table.to_s] || []
      next if rows.empty?
      next unless db.table_exists?(table)

      denorm = rows.map { |r| denormalize_row(db, table, r) }
      db[table].multi_insert(denorm) unless denorm.empty?
    end

    reseed_sequences(db, ordered)
  end

  filename
end

.normalize_row(row) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 192

def normalize_row(row)
  row.transform_values { |v| normalize_value(v) }
end

.normalize_value(value) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 174

def normalize_value(value)
  case value
  when Time
    value.utc.iso8601
  when DateTime
    value.to_time.utc.iso8601
  when Date
    value.iso8601
  when BigDecimal
    value.to_s("F")
  when Sequel::SQL::Blob
    { __blob__: Base64.strict_encode64(value) }
  else
    value
  end
end

.order_rows_by_self_fk(rows, pk_col, parent_col) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 236

def order_rows_by_self_fk(rows, pk_col, parent_col)
  return rows if rows.empty?
  return rows unless pk_col && parent_col

  by_id = {}
  rows.each { |r| by_id[r[pk_col]] = r }

  in_degree = Hash.new(0)
  children = Hash.new { |h, k| h[k] = [] }

  rows.each do |r|
    id = r[pk_col]
    parent_id = r[parent_col]
    next if parent_id.nil?
    next unless by_id.key?(parent_id)

    in_degree[id] += 1
    children[parent_id] << id
  end

  queue = rows.select { |r| in_degree[r[pk_col]].zero? }.map { |r| r[pk_col] }.sort

  ordered = []
  until queue.empty?
    id = queue.shift
    row = by_id[id]
    ordered << row if row

    children[id].sort.each do |child_id|
      in_degree[child_id] -= 1
      queue << child_id if in_degree[child_id].zero?
    end
  end

  # If cycle or missing nodes, append remaining deterministically.
  remaining_ids = by_id.keys - ordered.map { |r| r[pk_col] }
  remaining_ids.sort.each { |id| ordered << by_id[id] }

  ordered
end

.ordered_world_tables(db, only_tables: nil) ⇒ Object 



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# File 'lib/story_teller/snapshots.rb', line 83

def ordered_world_tables(db, only_tables: nil)
  tables = only_tables ? only_tables.map(&:to_sym) : world_tables(db)
  deps = table_dependencies(db, tables)
  topo_sort_tables(tables, deps)
end

.parse_value(value, type) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 198

def parse_value(value, type)
  return nil if value.nil?

  if value.is_a?(Hash) && value.key?(:__blob__)
    return Sequel::SQL::Blob.new(Base64.decode64(value[:__blob__]))
  end

  case type
  when :datetime, :timestamp
    value.is_a?(String) ? Time.iso8601(value) : value
  when :date
    value.is_a?(String) ? Date.iso8601(value) : value
  else
    value
  end
rescue ArgumentError
  # If parsing fails, keep original value to avoid hard failure.
  value
end

.primary_key_for_table(db, table) ⇒ Object 



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# File 'lib/story_teller/snapshots.rb', line 154

def primary_key_for_table(db, table)
  pk = db.primary_key(table)
  return pk if pk.is_a?(Symbol)

  # Fallback: detect first PK column from schema
  schema = db.schema(table)
  pk_cols = schema.map { |name, info| info[:primary_key] ? name : nil }.compact
  pk_cols.length == 1 ? pk_cols.first : nil
end

.read_snapshot_file(filename) ⇒ Object 



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# File 'lib/story_teller/snapshots.rb', line 69

def read_snapshot_file(filename)
  data = if gzipped?(filename)
    Zlib::GzipReader.open(filename, &:read)
  else
    File.read(filename)
  end

  JSON.parse(data, symbolize_names: true)
end

.reseed_sequences(db, tables) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 388

def reseed_sequences(db, tables)
  return unless db.database_type == :postgres

  tables.each do |table|
    next unless db.table_exists?(table)

    pk = primary_key_for_table(db, table)
    next unless pk

    max_id = db[table].max(pk)
    next unless max_id

    seq_row = db.fetch(SelectSerialSequence, table.to_s, pk.to_s).first
    seq_name = seq_row && seq_row[:seq]
    next unless seq_name

    db.run(format(SelectSetvalTemplate, sequence: db.literal(seq_name), max_id: max_id))
  end
end

.safe_foreign_key_list(db, table) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 148

def safe_foreign_key_list(db, table)
  db.foreign_key_list(table)
rescue Sequel::NotImplemented
  []
end

.self_fk_column(db, table) ⇒ Object 



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# File 'lib/story_teller/snapshots.rb', line 164

def self_fk_column(db, table)
  fks = safe_foreign_key_list(db, table)
  self_fk = fks.find { |fk| fk[:table].to_sym == table.to_sym }
  return nil unless self_fk

  cols = Array(self_fk[:columns])
  cols.length == 1 ? cols.first : nil
end

.table_dependencies(db, tables) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 93

def table_dependencies(db, tables)
  table_set = tables.to_h { |t| [t, true] }
  deps = {}
  tables.each { |t| deps[t] = {} }

  tables.each do |table|
    fks = safe_foreign_key_list(db, table)
    fks.each do |fk|
      parent = fk[:table]&.to_sym
      next unless parent
      next unless table_set[parent]
      next if parent == table # self-FK handled at row ordering level

      deps[table][parent] = true
    end
  end

  deps
end

.topo_sort_tables(tables, deps) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 121

def topo_sort_tables(tables, deps)
  remaining = tables.to_h { |t| [t, true] }
  incoming = deps.transform_values(&:dup)

  ordered = []
  loop do
    roots = remaining.keys.select { |t| incoming[t].empty? }.sort_by(&:to_s)
    break if roots.empty?

    roots.each do |root|
      ordered << root
      remaining.delete(root)
      incoming.delete(root)
      incoming.each_value { |parents| parents.delete(root) }
    end
  end

  return ordered if remaining.empty?

  cycle = remaining.keys.sort_by(&:to_s)
  raise "Foreign key table dependency cycle detected among: #{cycle.join(', ')}"
end

.truncate_tables(db, tables) ⇒ Object

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# File 'lib/story_teller/snapshots.rb', line 323

def truncate_tables(db, tables)
  if db.database_type == :postgres
    existing = tables.select { |t| db.table_exists?(t) }
    return if existing.empty?

    table_list = existing.map { |t| db.literal(t) }.join(", ")
    db.run("TRUNCATE TABLE #{table_list} RESTART IDENTITY CASCADE")
    return
  end

  # For other DBs, truncate/delete children first (reverse dependency order).
  tables.reverse_each do |table|
    next unless db.table_exists?(table)
    db[table].truncate
  end
end

.world_tables(db) ⇒ Object 



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# File 'lib/story_teller/snapshots.rb', line 79

def world_tables(db)
  db.tables.reject { |t| TableExclusions.include?(t) }
end